(1) Field of the Invention
The present invention relates generally to apparatus for the rapid freezing of food products, and more particularly to an improved method and apparatus for blast freezing and storage of food products.
(2) Description of Related Art
Traditionally, freezers and blast freezers in industrial plants have been separated. Freezers consist of refrigeration units having sufficient storage shelves, racks, and/or pallets for holding frozen product and maintaining the frozen product in a frozen condition. Freezers are found in a wide variety of sizes, from the small units forming a portion of a household refrigerator, to large walk-in rooms with over-head cranes, pallets, and forklifts for moving product about the room.
Blast freezers are specially designed freezers that are adapted to freeze unfrozen product within a shorter time period than simply placing the product into a traditional freezer. The blast freezing process has developed along several different lines in the prior art, but all utilize the flow of chilled gas as a component of the method. For example, U.S. Pat. No. 4,325,221 to Grewar discloses a method of freezing animal carcasses by first spraying the carcass with liquid nitrogen, and thence moving the carcass through a forced draught cooling system. Similarly, U.S. Pat. No. 4,367,630 to Bernard et al. discloses a system for rapidly chilling warm carcasses wherein the carcasses are first immersed in a cryogenic fluid and thence positioned in a chamber with sub-freezing gas circulated around the carcasses.
A continuous throughput blast freezer is disclosed in US Patent Application Publication No. 2003/0041614 to Burn, which uses a forced air chiller to rapidly freeze warm food products. Similarly, a forced air chiller is used to rapidly freeze food in U.S. Pat. No. 4,056,950 to Kaufman, Jr.; U.S. Pat. No. 5,452,588 to Onodera; and U.S. Pat. No. 5,826,432 to Ledbetter.
All of these patents disclose the use of a blast freezer in an area completely separate from storage areas for frozen food products. In most instances, the blast chamber is located in a completely different room, or within a separate enclosure sealed from the surrounding room. While this arrangement is effective for rapidly freezing the food products, it requires two separate sets of refrigeration equipment to operate—one set for the blast freezing process and one set for the storage of frozen food product. This use of two sets of refrigeration equipment is not only expensive to operate, but is also quite labor intensive for maintenance and repair considerations.